Abnormalities of total serum magnesium concentration

Transcription

1 J Vet Intern Med 2002;16: Prevlence nd Incidence of Serum Mgnesium Anormlities in Hospitlized Cts Jeffrey Toll, Hollis Er, Nichole Birnum, nd Thoms Schermerhorn Totl serum mgnesium concentrtion ([Mg 2 ] s ) ws prospectively determined for 57 cts dmitted to the intensive cre unit (ICU) of the Cornell University Hospitl for Animls. Dt were collected nd nlyzed to determine the following: prevlence nd incidence of [Mg 2 ] s normlities, medicl disorders ssocited with ltered [Mg 2 ] s, ssocition of ltered [Mg 2 ] s with other electrolyte normlities, length of hospitliztion for cts with normlities of [Mg 2 ] s versus those with norml [Mg 2 ] s, nd survivl of cts with norml [Mg 2 ] s versus those with norml [Mg 2 ] s. The point prevlence of mgnesium normlities ws 26%, the period prevlence ws 46%, nd the cumultive incidence ws 23%. Hypermgnesemi ws ssocited with normlities of serum potssium (P.04) nd phosphte (P.01) concentrtions. Anormlities of [Mg 2 ] s were not ssocited with norml serum concentrtions of N,C 2,orCl. On dmission, hypomgnesemi ws detected in cts with gstrointestinl, endocrine, nd other disorders; hypermgnesemi ws detected only in cts with renl disese, ostructive uropthy, or neoplstic disese. The medin hospitl sty for cts tht developed norml [Mg 2 ] s fter dmission ws longer thn for cts tht remined normomgnesemic (5 versus 4 dys, respectively; P.03). Despite the longer hospitl sty, the survivl of these cts ws lower thn tht of normomgnesemic cts (54 versus 77%; P.05). When ll cts were considered, the survivl of cts with norml [Mg 2 ] s lso ws decresed compred with normomgnesemic cts (62 versus 81%; P.05). We conclude tht normlities of [Mg 2 ] s my ffect moridity nd mortlity of ffected cts. Key words: Criticl cre; Feline; Moridity; Mortlity; Outcome ssessment; Potssium; Prospective study. Anormlities of totl serum mgnesium concentrtion ([Mg 2 ] s ), especilly hypomgnesemi, re common in criticlly ill humns. 1 5 The ssocition of hypomgnesemi with incresed mortlity in these ptients hs een documented y numer of clinicl studies. 6 8 An incresed prevlence of concurrent electrolyte normlities lso hs een documented in ptients with hypomgnesemi. 3,9 13 Furthermore, in some ptients, recognition nd tretment of hypomgnesemi were ssocited with improvement of hypoclcemi nd hypoklemi 3,11,13 nd resolution of crdic rhythm disturnces 10,14 tht hd een refrctory to conventionl therpy. Among the fctors ssocited with mgnesium deficiency in humns re poor nutrition, gstrointestinl disese, pncretitis, renl disese, endocrine disorders, nd dministrtion of common phrmcologicl gents, such s diuretics, some ntimicroils nd chemotherpeutics, nd insulin. 10 A clinicl investigtion hs suggested tht mgnesium normlities re common in hospitlized dogs. 15 Mrtin et l 15 showed incresed moridity, mortlity, nd prevlence of concurrent electrolyte disturnces in criticlly ill dogs with ltered [Mg 2 ] s when compred to normomgnesemic From the Deprtments of Clinicl Sciences (Toll, Birnum), Popultion Medicine nd Dignostic Sciences (Er), nd Moleculr Medicine (Schermerhorn), College of Veterinry Medicine, Cornell University, Ithc, NY. Dr Schermerhorn is presently ffilited with Knss Stte University, Mnhttn, KS. All work ws performed t the Cornell University Hospitl for Animls, New York Stte College of Veterinry Medicine, Cornell University, Ithc, NY. This work ws presented in prt t the 16th Annul Forum of the Americn College of Veterinry Internl Medicine, Sn Diego, CA, Reprint requests: Thoms Schermerhorn, VMD, Diplomte ACVIM, Deprtment of Clinicl Sciences, College of Veterinry Medicine, Knss Stte University, Mnhttn, KS ; e-mil: tscherme@vet.ksu.edu. Sumitted April 13, 2001; Revised August 14, 2001; Accepted Novemer 19, Copyright 2002 y the Americn College of Veterinry Internl Medicine /02/ /$3.00/0 counterprts. The purpose of this study ws to determine the prevlence nd incidence of ltered [Mg 2 ] s in hospitlized cts nd to determine whether ltered [Mg 2 ] s is ssocited with specific disese ctegories, concurrent electrolyte normlities, or incresed moridity nd mortlity. Mterils nd Methods Study Design A heterogeneous popultion of 67 cts consecutively dmitted to the intensive cre unit (ICU) y the medicl, surgicl, nd emergency services ws prospectively evluted for normlities of serum mgnesium concentrtion. Inclusion in the study required pretretment serum iochemicl nd electrolyte pnel on the dy of dmission nd serum electrolyte pnel on the finl dy of hospitliztion. The ICU t the Cornell University Hospitl for Animls houses criticlly ill ptients, ut medicl nd surgicl ptients tht require dvnced nursing cre, fluid therpy, nd close oservtion lso re dmitted. Cts dmitted to the ICU simply for oservtion or recovery from elective surgery were not included in the study. Pretretment concentrtions of serum electrolytes (sodium, chloride, potssium, clcium, mgnesium, nd phosphte) were mesured in ll cts on the dy of dmission nd gin on the finl dy of hospitliztion, which, for purposes of the study, ws the dy the ct ws dischrged from the ICU, died, or ws euthnized. Seril mesurement of electrolytes ws performed for some cts t the discretion of the ttending clinicin; these dt were included in the nlysis when pplicle. For sttisticl purposes, ech ct ws ssigned to one of the following disese ctegories on the sis of the principl dignosis: gstrointestinl, urogenitl, endocrine, neoplstic, or miscellneous (eg, crdic nd infectious). To provide internl control over the 6-month period of study, [Mg 2 ] s ws determined for 25 rndomly selected helthy cts tht were undergoing routine yerly exmintions. [Mg 2 ] s for ll of these cts ws within the reference rnge ( meq/l) estlished y the clinicl pthology lortory t the Cornell University Hospitl for Animls. Sttisticl Anlysis The point prevlence of norml [Mg 2 ] s t dmission (expressed s %) ws otined y dividing the numer of cts with norml [Mg 2 ] s t the time of dmission y the totl numer of cts in the

2 218 Toll et l Tle 1. Summry of mgnesium normlities in 57 hospitlized cts. Point prevlence Period prevlence Cumultive incidence 7 (12%) 16 (28%) 11 (20%) No. Affected Cts (%) Hypomgnesemi Hypermgnesemi 8 (14%) 10 (18%) 2( 4%) Overll 15 (26%) 26 (46%) 13 (23%) study. The period prevlence of norml [Mg 2 ] s ws otined y dividing the numer of cts with norml [Mg 2 ] s t ny time during the study (including those cts with [Mg 2 ] s normlities t dmission) y the totl numer of cts in the study. The cumultive incidence of norml [Mg 2 ] s ws otined y dividing the numer of cts with norml [Mg 2 ] s on dmission tht developed norml [Mg 2 ] s during hospitliztion y the totl numer of cts in the study. All susequent nlyses were performed with dt otined from initil dmission smples unless otherwise noted. Associtions etween norml [Mg 2 ] s nd disese ctegories were explored y performing simple cross-tultions nd clcultion of 95% confidence intervls on the percentges of cts in ech disese ctegory tht were hypomgnesemic or hypermgnesemic. Associtions etween norml [Mg 2 ] s nd normlities in the other serum electrolyte concentrtions were tested with Spermn s rnk correltion. Scoring for ech of the serum electrolytes ws s follows: 0 elow-norml serum concentrtion, 1 norml serum concentrtion, nd 2 ove-norml serum concentrtion. The ove method tested for ny correltion etween ct s [Mg 2 ] s nd either low, norml, or high serum concentrtion of the other electrolytes. If this method filed to detect correltion (ie, the result ws nonsignificnt), the cts with low serum electrolyte concentrtions were pooled with cts with high serum concentrtions (ie, cts with scores of 0 or 2 for the non-mg 2 electrolyte were comined). The correltion etween the 3 [Mg 2 ] s scores nd the new scoring for the other electrolyte (0 norml, nd 1 norml) then ws reclculted. This method llowed for the detection of ny correltion etween ct s [Mg 2 ] s nd either norml or norml concentrtions of the other electrolytes, ut it did not distinguish etween lower thn norml nd higher thn norml concentrtions of the non-mg 2 electrolyte. Use of the previous method ws reserved only for those ctegories in which there were multiple cts in oth the lower thn norml nd the higher thn norml ctegories for the other non- Mg 2 electrolyte, such tht pooling the 0 nd 2 scores might crete lrge norml ctegory tht wsn t lredy implicitly tested y the initil method. Finlly, the unconditionl ssocitions etween [Mg 2 ] s nd the 2 defined outcomes (totl dys hospitlized nd survivl to dischrge) were tested. Associtions etween the [Mg 2 ] s score (0 elow norml, 1 norml, nd 2 ove norml) nd totl dys hospitlized were tested with the Kruskl-Wllis test (1-wy nlysis of vrince for continuous dt tht cnnot e shown to e Gussin). Also, the 2-smple nonprmetric Wilcoxon rnk sum test ws used to seprtely compre 2 mesures, period prevlence nd cumultive incidence, to totl dys hospitlized. Associtions etween the [Mg 2 ] s score, period prevlence, cumultive incidence, nd survivl to dischrge from the hospitl were tested y simple chi-squre test. Confidence intervls on proportions were clculted y Epi Info 6. All other clcultions were done with Sttistix for Windows. Results Of 67 consecutive cts dmitted to the ICU during the study, 57 met the criteri for inclusion in the study. Dt from these 57 cts were susequently used for sttisticl Tle 2. Assocition of ny [Mg 2 ] s normlity with other electrolyte normlities. Electrolytes were scored for sttisticl nlysis either s 3-level scle (0 elownorml serum concentrtion, 1 norml serum concentrtion, nd 2 ove-norml serum concentrtion) or s 2-level scle (1 norml serum concentrtion, nd 0 norml serum concentrtion). Sodium Potssium Chloride Phosphte Clcium Other Electrolyte s 3-Level Scle Correltion P Vlue Other Electrolyte s 2-Level Scle Correltion 0.28 P Vlue [Mg 2 ] s, totl serum mgnesium concentrtion. Correltion to norml serum potssium (either hypo-or hyperklemi). Correltion to hyperphosphotemi. nlysis. Cts were divided ccording to primry disese into the following 5 disese ctegories: neoplstic (n 12), gstrointestinl (n 19), urogenitl (n 12), endocrine (n 7), nd miscellneous (n 7). The point prevlence, period prevlence, nd incidence of hyper- nd hypomgnesemi re shown in Tle 1. The point prevlence of norml serum mgnesium concentrtion t the time of dmission ws 26% (n 15). Of ll cts, 12% (n 7) were hypomgnesemic, nd 14% (n 8) were hypermgnesemic. The period prevlence (ie, the percentge of cts tht hd n norml [Mg 2 ] s t ny time during hospitliztion) ws 46%. Of ll cts, 28% (n 16) hd hypomgnesemi, nd 18% (n 10) hd hypermgnesemi. The cumultive incidence of mgnesium disorders (the percentge of cts with norml [Mg 2 ] s t dmission tht developed n norml [Mg 2 ] s during hospitliztion) ws 23% (n 13). Of ll cts, 20% (n 11) developed hypomgnesemi, nd 4% (n 2) developed hypermgnesemi. When ll cts were considered, hypermgnesemi ws ssocited with hyperklemi nd hypoklemi (P.04) nd hyperphosphotemi (P.01). Anormlities of [Mg 2 ] s were not ssocited with norml serum concentrtions of sodium, clcium, or chloride (Tle 2). On dmission, hypomgnesemi ws detected in cts in the gstrointestinl, endocrine, nd miscellneous disese ctegories; hypermgnesemi ws detected only in cts with urogenitl or neoplstic disese. The numer of cts nd the period prevlence of mgnesium normlities in ech disese ctegory re shown in Tle 3. The dt indicte tht the period prevlences of serum mgnesium normlities for ech of the disese ctegories (which rnged from 32 to 57%) pproximtely reflected the comined period prevlence of 46%, s shown in Tle 1. In ddition, point prevlent (present t dmission) nd incident (developed during hospitliztion) cses of serum mgnesium normlities ech ccounted for pproximtely 50% of the totl numer of cts in ech ctegory (dt not shown). Cts with endocrine disese were exceptions to the generl trend. Ech of the 4 ffected cts in the endocrine disese ctegory hd dietes.04

3 Serum Mgnesium in Cts 219 Tle 3. Summry of mgnesium normlities in 57 hospitlized cts ctegorized y disese. Neoplsm Endocrine Gstrointestinl Urologicl Miscellneous Cts in Ech Ctegory: n (% totl study cts) 12 (21) 7 (12) 19 (33) 12 (21) 7 (12) Cts with Anorml [Mg 2 ] s :n (% totl cts in ctegory) 6 (50%) 4 (57%) c 6 (32%) 6 (50%) 3 (43%) The totl numer of cts with n norml totl serum mgnesium concentrtion ([Mg 2 ] s ) listed (n 25) is less thn the totl numer of ffected cts presented in Tle 1 (n 26). Only dmission dt from 1 ct tht ws hypermgnesemic on dmission nd susequently ecme hypomgnesemic re included in Tle 3. However, dmission nd hospitliztion dt for this ct were included in prevlence nd incidence clcultions presented in Tle 1 nd 4. Three of these cts hd hypermgnesemi; ll 3 cts lso hd pleurl effusion nd thorcic neoplsm. c These 4 cts ll developed hypomgnesemi while hospitlized. All 4 were dietic nd hd presented with dietic ketocidosis. mellitus nd presented to the hospitl with dietic ketocidosis. All of these cts hd norml [Mg 2 ] s on dmission nd susequently developed hypomgnesemi during tretment. The medin hospitl sty for cts tht developed norml [Mg 2 ] s while hospitlized ws longer thn for cts tht remined normomgnesemic (5 dys versus 4 dys, respectively; P.03) (Tle 4). The survivl of cts tht developed mgnesium disorders (ie, the incident cses) ws decresed when compred with normomgnesemic cts (54% versus 81%; P.05). When ll cts were considered (ie, prevlent nd incident cses were comined), the survivl of cts with mgnesium disorders lso ws decresed when compred with normomgnesemic cts (62 versus 81%; P.05). Discussion Our results indicte tht normlities of [Mg 2 ] s re common in hospitlized cts. Nerly 50% of the cts in our study hd n [Mg 2 ] s mesurement outside the reference rnge t lest once during hospitliztion. Anormlities of [Mg 2 ] s were relevnt to ptient mngement nd were ssocited with incresed moridity nd mortlity in ffected cts. Mgnesium disturnces lso were ssocited with normlities of serum potssium nd phosphte concentrtions. Cts with mgnesium normlities lso hd longer period of hospitliztion nd were more likely to die or e euthnized thn cts tht remined normomgnesemic. Hypomgnesemi ws more common thn hypermgnesemi in this study. At the time of dmission to the ICU, 12% of cts were hypomgnesemic. Of the cts tht were normomgnesemic t dmission, nerly 20% eventully developed hypomgnesemi during hospitliztion. The prevlence nd incidence of hypomgnesemi in this popultion of cts were similr to those reported for humns 1 4,6 nd dogs. 15 The high incidence of hypomgnesemi in hospitlized humn ptients hs een ttriuted to severl cuses, including decresed dietry intke, dministrtion of certin drugs (eg, diuretics, minoglycosides, nd chemotherpeutics), nd infusion of crystlloid fluids with indequte mgnesium content. 6,10,16 Similr fctors likely contriuted to the development of hypomgnesemi in the hospitlized cts descried in this study. Most cts in this report received IV therpy, nd the mjority received lctted Ringer s solution, which is mgnesium free. Nerly ll of the study cts received mediction in ddition to prenterl fluids; some of the drugs used hve een implicted s potentil cuses of hypomgnesemi in humns, including diuretics, minoglycosides, nd chemotherpeutic drugs. The smll numer of individul cts tht received prticulr drug prohiited specific nlysis of ny 1 drug s role in inducing hypomgnesemi in this study. Indequte dietry intke of mgnesium ws nother prole cuse of hypomgnesemi for some of the cts in this study, ut detiled nutritionl records were not ville for ll cts. Five cts received nutritionl support vi nsogstric or esophgel tue feeding or totl prenterl nutrition (TPN). Two of these 5 cts (1 ct treted y TPN nd 1 y enteric feeding) developed hypomgnesemi shortly fter nutritionl cre ws initited. The TPN formultion ws supplemented with vitmins nd trce minerls, which included mgnesium, nd ws considered mgnesium replete. A decrese in [Mg 2 ] s hs een reported s component of the refeeding syndrome, 17 nd the initition of nutritionl cre might hve induced similr chnges in these cts. We found tht hypomgnesemi, lthough common in hospitlized cts, generlly ws not ssocited with ny specific ctegory of disese. A similr finding ws reported in study of dogs. 15 The numer of cts studied my hve een too smll to detect n ssocition of this type. Another plusile explntion is tht hypomgnesemi occurred most often in those cts tht were the most seriously ill. Accordingly, pproximtely 50% of the ffected cts in ech disese ctegory hd hypomgnesemi (Tle 1). An exception to the generl trend occurred in cts with endocrine disese. All 4 of the cts with norml [Mg 2 ] s hd norml [Mg 2 ] s when presented, ll developed hypomgnesemi while hospitlized, ll were dietic, nd ll hd Tle 4. Durtion of hospitliztion nd mortlity for cts with [Mg 2 ] s disorders. Anorml [Mg 2 ] s Norml [Mg 2 ] s P Vlue Medin hospitliztion sty (dys) Dischrged from ICU (% of cts) Prevlent cses Incident cses Prevlent cses Incident cses ICU, intensive cre unit; [Mg 2 ] s, totl serum mgnesium concentrtion; Prevlent, cts with [Mg 2 ] s disorders t ny time during hospitliztion; Incident, cts tht developed norml [Mg 2 ] s while hospitlized.

4 220 Toll et l ketocidosis. These findings re consistent with those from recent report of [Mg 2 ] s normlities in dietic cts, which demonstrted tht [Mg 2 ] s decresed over time in cts treted for dietic ketocidosis. 18 Overll, the finding tht cts tht hd mgnesium disturnces were more likely to die efore dischrge from the ICU supports the notion tht [Mg 2 ] s normlities occur primrily in cts tht re very ill. Studies hve shown tht the most criticlly ill humns re lso the most likely to develop hypomgnesemi, regrdless of their principl dignosis. 1,6 Hypermgnesemi in cts, s in humns, usully results from renl insufficiency or urinry ostruction. 19,20 The mjority of cts with hypermgnesemi in this study hd renl or postrenl zotemi. Of the 13 cts tht developed norml [Mg 2 ] s during hospitliztion, only 2 developed hypermgnesemi. Hypermgnesemi developed concurrently with cute renl filure nd zotemi in oth of these cts. All of the cts in our study with postrenl zotemi hd concurrent hypermgnesemi, which is common finding in cts with urinry ostruction. 20 Relief of urethrl ostruction resulted in prompt resolution of hypermgnesemi nd zotemi in ll cts in our study. All hypermgnesemic cts tht were not zotemic hd 2 common fetures: thorcic neoplsi nd pleurl effusion. Of the 12 cts with neoplsi tht were included in the study, only 3 were hypermgnesemic t dmission. All 3 of these cts hd thorcic neoplsi (1 ech with lymphom, mesotheliom, nd crcinom). These cts hd not received ny therpy efore hospitl dmission, nor hd thorcocentesis een performed. The mechnism underlying the development of hypermgnesemi in these cts is unknown, ut the phenomenon wrrnts further study. Anormlities of [Mg 2 ] s hve well-documented ssocitions with other electrolyte disturnces in humn ptients Our results show tht some of the sme ssocitions etween electrolyte disturnces lso occur in cts. The finding tht hypermgnesemi is ssocited with hyperphosphtemi in cts is not unexpected ecuse oth normlities develop s result of renl insufficiency. With the exception of the 3 cts with neoplsi, ll hypermgnesemic cts in this study lso hd zotemi. Hypermgnesemi ws oserved in zotemic cts with hyperklemi nd in cts with hypoklemi. The ltter findings most likely reflected the nture of the zotemi (ie, cute versus chronic renl filure). There is well-documented ssocition etween hypomgnesemi nd oth hypoklemi nd hypoclcemi in humns, 3,9 13 ut similr ssocition ws not detected in the cts of this study. We found tht cts with either hypermgnesemi or hypomgnesemi hd incresed moridity nd mortlity reltive to cts with normomgnesemi. For the purposes of this study, moridity nd mortlity mesures were relted to the ICU. We used the numer of dys spent in the ICU s mesure of moridity nd successful dischrge from the ICU s the mesure of survivl. The numer of dys spent in the ICU ws chosen s the mesure of moridity ecuse it reflects individul ptient fctors, ny of which could ffect ptient moridity, such s severity of illness, need for intensive medicl therpy or nursing cre, nd the client s expense. None of the cts reported in this study were kept in the ICU for the specific purpose of correcting norml [Mg 2 ] s. Anorml [Mg 2 ] s (either hypo- or hypermgnesemi) tht developed fter dmission to the ICU ws ssocited with prolonged hospitliztion. Eleven of the 13 normomgnesemic cts tht developed norml [Mg 2 ] s while hospitlized developed hypomgnesemi; only 2 cts developed hypermgnesemi. The development of hypomgnesemi in hospitlized cts proly is multifctoril. Among the fctors tht might contriute to mgnesium depletion in these cts re decresed dietry mgnesium intke, use of drugs tht promote hypomgnesemi, nd fluid therpy with mgnesium-deficient fluids. The role of tretment fctors in the development of hypomgnesemi ws not ddressed y this study. Regrdless of the inciting fctor(s), the clinicl condition of ct tht developed [Mg 2 ] s normlities improved more slowly thn tht of normomgnesemic ct in this study, nd it ws longer efore these ptients were judged well enough to e sfely dischrged from the ICU. Cts with hyper- or hypomgnesemi lso were more likely to die or e euthnized thn cts tht remined normomgnesemic. Two cts developed hypermgnesemi s result of cute renl filure tht occurred during hospitliztion. Both of these cts were euthnized ecuse of refrctory oliguri nd deteriorting physicl condition. Poor renl function ws more relevnt to mortlity in these cts thn ws hypermgnesemi. The reltionship of hypomgnesemi to mortlity is less cler. In criticlly ill humns, hypomgnesemi is ssocited with incresed mortlity, regrdless of the principl dignosis. 6 In mny cses, the underlying disorder my e more relevnt to outcome thn hypomgnesemi, s in the cts with oliguric renl filure nd hypermgnesemi. Hypomgnesemi, however, could cuse mortlity y promoting or excerting crdic dysfunction, neuromusculr wekness, nd concurrent electrolyte imlnce, s reported in humn ptients. 16 The physiologicl consequences of hypomgnesemi lso could increse the moridity nd mortlity of ffected cts y prolonging hospitliztion or y incresing client expense nd necessitting euthnsi for economic resons. It is uncertin whether or not specific mesures to prevent or tret hypomgnesemi hve fvorle effect on moridity nd mortlity, ut such n effect is supported y our dt. Susequent oservtions hve indicted tht tretment with mgnesium-contining fluids c my decrese the incidence of hypomgnesemi in cts (unpulished dt). Certin spects of the study design deserve comment. Inclusion in this study ws not determined y the severity of the cts illness ut only y their dmission to the ICU. In humns, the mesurement of the severity of illness is routinely used for clinicl decision mking nd ssessment of performnce of individul tretment units. 21 One such method, which hs een widely pplied, is known s the Acute Physiology nd Chronic Helth Evlution (APACHE) scoring system. 22 APACHE scores hve direct correltion with prmeters such s [Mg 2 ] s nd mortlity in humns. 1,6 However, similr physiologicl scoring systems for cts re not yet routinely used, nd the systems used in humn ptients my not e vlid for use in cts. Strtifiction of the study cts y physiologicl scoring

5 Serum Mgnesium in Cts 221 system might hve een more useful for detecting correltions etween severity of illness nd ltered [Mg 2 ] s. Our results lso were ffected y owner decisions out euthnsi. Our results did not discriminte etween nonsurvivors tht died or were euthnized, ut the mjority of cts clssified s nonsurvivors were euthnized. The designtion of euthnized ptients s nonsurvivors could hve influenced our results, ecuse some of these cts my hve survived with dditionl tretment. The inclusion of euthnized ptients in the nonsurvivor group is justifile, however, ecuse the decision to recommend euthnsi is influenced y the ptient s dignosis, clinicl condition, prognosis, nd response to therpy, in ddition to finncil resources. Totl [Mg 2 ] s, rther thn ionized mgnesium concentrtion, ws mesured in the cts in this study. The est mesure of mgnesium sttus in ny species is controversil. As with clcium, the ionized mgnesium concentrtion my e of greter physiologicl importnce thn totl [Mg 2 ] s, ut this issue is not yet resolved. 14 Assessment of mgnesium sttus y methods other thn totl [Mg 2 ] s hs not yet ecome widely ccepted, nor hs the clinicl utility of such methods een estlished in nimls. Similr to potssium, norml [Mg 2 ] s my not e n ccurte reflection of the totl ody concentrtion of the ion. 19 It is likely, however, tht once hypomgnesemi is detected, whole-ody mgnesium depletion hs occurred. 16 Assessment of totl [Mg 2 ] s is currently considered the gold stndrd for ssessment of disorders of mgnesium in humns. 12 In conclusion, this study hs demonstrted tht norml [Mg 2 ] s is common in criticlly ill cts nd is ssocited with incresed moridity nd mortlity. Routine mesurement of [Mg 2 ] s in hospitlized cts is recommended nd my provide prognostic informtion to clinicins. Future studies to determine the enefit of prevention nd tretment of mgnesium disorders my help extend some of the findings of this study. Footnotes Epi Info 6, Version 6.04, USDHHW, Centers for Disese Control nd Prevention, Atlnt, GA Sttistix for Windows, Anlyticl Softwre, Tllhssee, FL c Plsm-Lyte, Bxter, Deerfield, IL Acknowledgments The uthors thnk Dr Jmes Richrds for support nd encourgement nd Dr Trcy Stokol for estlishing the reference rnge of cts for serum mgnesium concentrtion. This study ws supported y reserch grnt from the Cornell Feline Helth Center. References 1. Lum G. Hypomgnesemi in cute nd chronic cre popultions. Am J Clin Pthol 1992;97: Reinhrt RA, Desiens NA. Hypomgnesemi in ptients entering the ICU. Crit Cre Med 1985;13: Ryzen E, Wgers PW, Singer FR, Rude RK. Mgnesium deficiency in medicl ICU popultion. Crit Cre Med 1985;13: Whng R, Ryder KW. Frequency of hypomgnesemi nd hypermgnesemi. J Am Med Assoc 1990;263: Chernow B, Bmerger S, Stoiko M, Vdnis M. Hypomgnesemi in ptients in postopertive intensive cre. Chest 1989;95: Rueiz GJ, Thill-Bhrozin M, Hrdie D, Crlson RW. Assocition of hypomgnesemi nd mortlity in cutely ill medicl ptients. Crit Cre Med 1993;21: Cnnon LA, Heiselmn DE, Dougherty JM, Jones J. Mgnesium levels in crdic rrest victims: Reltionship etween mgnesium levels nd successful resuscittion. Ann Emerg Med 1987;16: Broner CW, Stidhm GL, Westenkirchner DF, et l. Hypermgnesemi nd hypoclcemi s predictors of high mortlity in criticlly ill peditric ptients. Crit Cre Med 1990;18: Kingston ME, Al-Si i MB, Skooge WC. Clinicl mnifesttions of hypomgnesemi. Crit Cre Med 1986;14: Tso EL, Brish RA. Mgnesium: Clinicl considertions. J Emerg Med 1992;10: Hmil-Ruth RJ, McGory R. Mg 2 repletion nd its effect on K homeostsis in criticlly ill dults: Results of doule-lind, rndomized, controlled tril. Crit Cre Med 1996;24: Whng R, Whng DD, Ryn MP. Refrctory K depletion: A consequence of Mg 2 deficiency. Arch Intern Med 1992;152: Whng R, Oei TO, Aikw JK, et l. Predictors of clinicl hypomgnesemi. Hypoklemi, hypophosphtemi, hypontremi, nd hypoclcemi. Arch Intern Med 1984;144: McLen RM. Mgnesium nd its therpeutic uses: A review. Am J Med 1994;96: Mrtin LG, Mtteson VL, Wingfield WE, et l. Anormlities of serum mgnesium in criticlly ill dogs: Incidence nd implictions. J Vet Emerg Crit Cre 1994;4: Whng R, Hmpton EM, Whng DD. Mgnesium homeostsis nd clinicl disorders of mgnesium deficiency. Ann Phrmcother 1994;28: Brooks MJ, Melnik G. The refeeding syndrome: An pproch to understnding its complictions nd preventing its occurrence. Phrmcotherpy 1995;15: Norris CR, Nelson RW, Christopher MM. Serum totl nd ionized mgnesium concentrtions nd urinry frctionl excretion of mgnesium in cts with dietes mellitus nd dietic ketocidosis. J Am Vet Med Assoc 1999;215: Reinhrt RA. Mgnesium metolism A review with specil reference to the reltionship etween intrcellulr content nd serum levels. Arch Intern Med 1988;148: Drotz KJ, Hughes D. Concentrtion of ionized clcium in plsm from cts with urethrl ostruction. J Am Vet Med Assoc 1997; 211: Nouir S, Belghith M, Eltrous S, et l. Predictive vlue of severity scoring systems: Comprison of four models in Tunisin dult intensive cre units. Crit Cre Med 1998;26: Knus WA, Zimmermn JE, Wgner DP, et l. APACHE Acute Physiology nd Chronic Helth Evlution: A physiologiclly sed clssifiction system. Crit Cre Med 1981;9: